Equine Coronavirus Identified in European Horses

It started in a diarrheic foal in North Carolina in 1999. A few years later, researchers found it in Japan. Today, scientists have discovered the virus in Europe. And what’s more, they’ve found it in horses' respiratory fluid, whereas before, it’s only been isolated in feces.

What is this new, traveling virus? It’s equine coronavirus, also known as ECoV. ECoV is rarely fatal, but it can cause significant pain and discomfort in horses, mainly through fever and diarrhea. And unfortunately, French researchers recently determined that the disease appears to be on the move.

“ECoV had only been identified in the United States and Japan, but our study makes us think that the virus is circulating more widely on an international level,” said Fabien Miszczak, PhD, of the University of Caen's Virology Laboratory, in Normandy, France.

Miszczak and his fellow researchers tested 595 laboratory samples from French horses suffering from enteric (intestinal) or respiratory illness, he said. Twelve of these samples were positive for ECoV. While 11 of the samples were from feces, one was from respiratory fluid.

“Our study has shown, for the first time, the presence of the ECoV virus in a respiratory sample,” Miszczak said.

That sample was taken from a 9-month-old foal with respiratory symptoms, he said. However, it’s not possible to know whether the virus was the actual cause of those signs.

Most of the other positive samples came from foals with diarrhea, but two fecal samples came from the same adult horse—at five-week intervals. Previously, researchers in the United States and Japan had found that the virus only remained present in fecal material for three to nine days, he said.

“Our findings indicate a viral replication that is intense and persistent, hence the presence of potentially severe clinical forms,” Miszczak and his team reported in their study.

Severe enough, in fact, to cause death. This particular horse with the two positive fecal samples died from complications of diarrhea, Miszczak said.

Even so, the study results are not cause for alarm among European horse owners, Miszczak said: “At this time, ECoV does not seem to be a threat for European horses. The most recent studies indicate that the virus is present in our territories (United States, Japan, and France) and is circulating at a low level in the equine population.

“However, from what we know of coronavirus in humans, it’s possible that the virus could suddenly emerge and cause epidemics,” he added. “So owners should be aware of it and should isolate symptomatic horses, especially foals younger than 6 months old.”

The disease might have entered Europe through equine transportation, as ECoV is not a reportable disease, and testing for it is not required for import and export, Miszczak said.

Upcoming studies will focus on a screening of France's general horse population to better understand the seroprevalence of the virus throughout the country, he said.